public class offer10_11 {
    public int numWays(int n) {
        int num = 0,num1 = 1,num2 = 1;
        for(int i =0;i < n; i ++) {
            num = (num1 + num2) % 1000000007;
            num1 = num2;
            num2 = num;
        }
        return num1;
    }
}
